Nonwoven materials may be used as wet wipes. Typically, wet wipes are stacked in a container in either a folded or unfolded configuration. For example, containers of wet wipes are available wherein each of the wet wipes are arranged in a folded configuration, such as c-folded, z-folded, or quarter-folded configurations, which are well known to those skilled in the art. Sometimes the folded wet wipes are also interfolded with the wet wipes immediately above and below in the stack of wet wipes. In yet other configurations, the wet wipes are placed in the container in the form of a continuous nonwoven material. In this case, each individual wet wipe or sheet may be connected, from the first sheet to the last, by similarly weakened lines of perforations or by adhesive bonds. These wet wipes can be stacked on top of each other in a fan folded manner or can be wound into a roll configuration.
Often, nonwoven substrates are used to produce wet wipes due to their desirable properties and low cost of manufacture. Historically, these nonwoven substrates have been non-dispersible, focusing on the strength of the nonwoven during use as an attribute. Recently, more emphasis is being placed on providing wet wipes having the ability to disperse when disposed of in the toilet bowl after use. Several municipalities have banned the disposal of non-dispersible wet wipes in municipal sewer systems. The non-dispersible wet wipes can plug typical sewage handling components such as pipes, pumps, lift stations, or screens causing operational issues for the treatment plant.
Unfortunately, when nonwoven materials have been employed as wet wipes, dispensing of the wet wipes has not been completely satisfactory. Unsatisfactory dispensing has been encountered, particularly in the case of wet wipes that are formed from adhesively-bonded nonwoven materials. Poor dispensing can be ascribed to a variety of factors, one of which is sheet-to-sheet adhesion, which is addressed herein.
Sheet-to-sheet adhesion is the tendency of a wet wipe to adhere to itself or adjacent wet wipes. Sheet-to-sheet adhesion can be attributed to a number of factors, some of which include compression of stacked or rolled wet wipes during manufacturing, attractive interactions between the nonwoven material and a liquid wipe composition, and interactions between the surfaces of adjacent, contacting nonwoven wet wipes. If the sheet-to-sheet adhesion is sufficiently high, single-handed, one-at-a-time dispensing of the wet wipes can be problematic. This problem can be particularly acute when the individual wet wipes in the stack are folded such that the leading edge of each wet wipe is folded over another portion of the wet wipe. If the leading end edge of the wet wipe has a high affinity for the wet wipe underlying it (high sheet-to-sheet adhesion), it can be undesirably difficult for the user to identify and grasp the leading end edge and peelingly lift it from the underlying stack of wet wipes. If the sheet-to-sheet adhesion is sufficiently high, tearing of the wet wipe can occur when attempting to remove the leading wet wipe from the top of the wet wipe stack.
Moreover, when the user removes an individually folded wet wipe from the underlying stack, high sheet-to-sheet adhesion can result in undesirable incomplete unfolding of the wet wipe. Additionally, high sheet-to-sheet adhesion can cause an individual folded wet wipe to remain partially adhered to the adjacent wet wipe, upon which it is resting, thus causing dispensing of multiple wet wipes rather than the preferred dispensing of an individual wet wipe. Such difficulties in separation and incomplete unfolding have undesirably resulted in reduced consumer acceptance.
This sheet-to-sheet adhesion issue has been previously addressed for various types of wet wipes. For example, non-dispersible wet wipes have been prepared with improved dispensability, wherein the leading edge of the wet wipe utilizes a repeating non-linear pattern (such as a sinusoidal pattern) to facilitate a reduced peel force for dispensing. Other non-dispersible wet wipes have also been prepared with improved dispensability wherein the coefficient of friction is reduced on the wet wipe surfaces through embossing or chemical means. Dispersible wet wipes have also been prepared that include a separate coating process with anti-blocking coatings to reduce sheet-to-sheet adhesion and facilitate a reduced peel force for dispensing.
Unfortunately, these approaches to addressing the dispensing problems caused by sheet-to-sheet adhesion are not sufficient to counteract the considerably higher sheet-to-sheet adhesion that can be observed when the wet wipe is in a stacked and/or folded configuration. Particularly, the use of an anti-blocking coating is problematic as it requires the use of an additional manufacturing step thereby increasing manufacturing complexity and cost. Additionally, changes to the physical structure of the wipes increase costs and the complexity of the process. Thus, there is a need to provide a wet wipe having a liquid wipe composition that provides reduced sheet-to-sheet adhesion without the need for additional steps in the process.